basic PHP variable local/global issue - php

Question

I have come from a background of C++ and am relatively new into the world of PHP.
I'm currently writing a little piece that has an index.php and definitions.php.
In definitions I have the variable
$passfile = "../ass1_data/passwords.txt";
I want to use $passfile inside a function in my index.
Can I just use it $passfile or do I have to use global with it as well?
This is what I have
function checkPasswd($login,$passwd){
global $passfile;
$p = $passfile;
foreach ($p as $line) {
// some code
}
}
At the moment I am getting the error 'Invalid argument supplied for foreach()'
Any help or explanations would be appreciated, thank you.

Answer 1

Assuming the text file contains lines with passwords in it you need to read the contents of the file in first and then loop through the results:
$passfile= file('../ass1_data/passwords.txt');
function checkPasswd($login,$passwd){
global $passfile;
foreach ($passfile as $line) {
// some code
}
}

Answer 2

1- you have to use global keyword for using global variable inside functions.
2- for second case(foreach) first you have to read the file, then use explode function to split it and use it in foreach.:
$passfile = "../ass1_data/passwords.txt";
function checkPasswd($login,$passwd){
global $passfile;
$p = explode("\n",file_get_contents($passfile));
foreach ($p as $line) {
// some code
}
}

Answer 3

You can't simply foreach over a string (even though you can access its bytes with subscript notation).
You need to turn it into an array first, one option for doing that is explode("\n").
However, it sounds like you want to open the file at that location. In that case, you can use file(), which will automatically provide you with an array of lines in that file.